An offshore facility such as a wind turbine mounted on an offshore support structure requires a transmission link to other offshore facilities, such as other wind turbines, a substation, etc. Usually, a transmission cable arrangement between two such facilities rests on the seabed. To this end, the transmission cable arrangement is suspended from a platform or intermediate level, usually referred to as a “transition piece”, at the base of the wind turbine tower to the seabed. Such a transmission cable arrangement can comprise a number of power transmission cables arranged in a tube or hose. To protect the transmission cable from excessive bending, a rigid curved steel tube (usually referred to as a “J-tube” on account of its shape) is usually arranged between the transition piece and the base of the offshore support structure to ensure that the bending radius of the transmission cable is acceptable. At the lower end of the J-tube, the transmission cable emerges and lies on the seabed. However, a problem arises when the seabed is scoured away at the base of the offshore structure, for example as a result of tidal forces. It may happen that the seabed is scoured away from underneath the end of the J-tube to such an extent that the J-tube exit is now higher than the seabed, so that the transmission cable is forced to bend sharply downward at the J-tube exit. The transmission cable may become damaged as a result, and costly repairs may ensue. For this reason, the lower portion of such a rigid J-tube is usually flushed into the seabed, so that it is buried under sand. However, it is difficult to predict the correct length for such a J-tube and to predict the extent of scouring that may arise over time, so that flushing the J-tube end section into the seabed is not a reliable solution.
Another disadvantage of the known approaches is that divers are required to assist the loading of the transmission cable into the J-tube, so that the initial construction costs are relatively high. The J-tube must be securely connected to the support structure, usually by welding. However, weld points can also be prone to failure over time and may require costly repairs. Furthermore, a transmission cable must be pulled into a rigid J-tube already in place between the support structure and the seabed. Damage to the transmission cable can result as it is pulled up through the curved end section of the rigid steel J-tube. For example, an otherwise circular cross-sectional shape of a transmission cable can become flattened by distortion when undue force is exerted during the loading or pulling procedure.